Gordian Knot.

Gordian Knot (Γόρδιος δεσμός) (Nodus Gordianus) was a very difficult knot in Greek myths and legends.

Phrygia (Φρυγία) (Phrygía) was a kingdom without king. Simple man named Gordias (Γορδιάς, Γόρδιος) (Gordias, Gordius) became a king of Phrygia. He called the capital after himself: Gordion (Γόρδιον) (Górdion, Gordium). Also, Gordias created the knot.

Alexander the Great cut the Gordian knot.

There is a metaphor that means solve difficult problem about the Gordian Knot.